What’s the most powerful number in automotive marketing? No, not zero, as in “zero down, zero percent interest”… the answer we’re looking for is 40, as in “40 MPG hwy.” With the compact segment heating up, 40 MPG on the highway is very nearly a price of entry… if your base model doesn’t achieve the magic number, you’d better have a special edition that does. But even as “40 MPG” becomes more and more important as an industry benchmark, it inevitably raises a perennial question: do EPA numbers mean anything in the real world? Hyping the highest possible number rather than a “combined” figure is a classic marketing move, but one that risks exposing the EPA highway number as a meaningless metric. And if nobody actually gets the rated efficiency, it’s only a matter of time before the market begins to demand more accurate reporting.

At the Mazda3 launch in Los Angeles, the company conducted informal but revealing real-world mileage observations on its own cars and five leading rivals.

As driven by the media over a mixed bag of city, highway and even mountain driving conditions, the following overall mpg results were obtained: Civic, 34.5; Mazda3, 33.7; Focus, 32.1; Corolla, 30.7; Elantra, 29.9; and Cruze, 29.8. While hardly scientific, these numbers do underscore the fact the 40 mpg figure is an illusion.

Is the only way to get 40 MPG highway in a diesel or hybrid? Or have any of you, TTAC’s Best and Brightest, recorded 40 MPG in one of the new generation of gas-powered compacts or subcompacts? How gingerly do you have to drive to match EPA highway numbers? Are some cars closer than others? Is it time to pressure marketers to switch to a combined MPG number, or will that be just as misrepresentative?

My 2004 Saturn Ion coupe gets34-35 every tankful. This is mostly highway, 30 mile each way commuting. I try to keep it at 60 all the way, drive gently all the way…It’s fun for me to see how high my average MPG goes, and also fun to laugh at all the folks driving their Suburbans at 75 and wondering why they only get 12 MPG.

Tire pressures and alignment with a conservative throttle along with key off at drive thru and longer stoplights works the best. Come winter time it’s probably 10-30% above EPA highway.I can exceed EPA highway from 20-40% with a brake-in miles and a few tweaks. Twenty percent for V8’s and 40-percent for 4-cylinders. On my daily 119 mile commute.

Yup – I’ve got a 2006.5 Scion XB. I average about 31-32mpg with the cruise glued to 72. I’d read a lot about people doing far better, so I gave it a go exactly one time on a long, solo drive. There was little to no traffic, so I kept the speedo between 55-60mph for an entire tank of gas… When I did the math, I averaged 45.5 mpg. No hypermiling bullshit, just driving about 55 on a lonely highway at night.

Impressive, but not surprising for a 2400# car with 101 horsepower! Aerodynamics are no joke above 55, especially when you’re driving a toaster. As much as I enjoyed the crazy good mpg that one time, a trip to the in-laws would take a full 2 hours longer at 55mph. Never gonna do it, not with a toddler in the car. 72mph, and 32mpg it is.

I too got a 41mpg figure once on my ’05 xB. I was even hauling 600lbs of car suspension parts. I accomplished this feat by riding a truck’s wake and hypermiling the hell out of it, since I couldn’t find an open gas station. This was also on I-80 in Iowa on a section with few hills. I spent every drop of fuel on the highway. The mpg figure is subject to many variables. Makes you wonder. I have never been able to replicate that trip. The car usually gets between 29-34mpg on average. It also seems to “wake up” when it’s weened off the E10 squirrel piss gas we are forced to use here in IL as well, gaining an extra 2mpg’s.

These companies should put a disclaimer on these lofty 40 mpg figures, like: “Your actual numbers will most likely be lower” Pretty soon even full size cars are gonna advertise 40 mpg numbers, coasting downhill with engine off

That magic highway number is almost meaningless. If you drove 100% of your driving on thehighway, yeah, you could probably expect to get that. But who does that?? I can reset my the trip computer in my 2011 Sonata when I leave work, and have it show my 41 mpg by the time I coast of my exit, but what does that prove?

People should expect to get somewhere in between the city and highway ratings. How close to which one depends on driving habits.

Aren’t the new EPA window stickers coming next year going to emphasize the combined mpg rating instead of the city/highway?

I think EPA numbers are optimistic in the city and pessimistic on the highway. For example, my 2005 Mazda3 is rated 21/26 under the new system – but in city driving I usually average 18 to 20mpg while on a tank that’s only 60-70% highway I can get 27. Looking at, say, Consumer Reports’ real-world figures, this applies to many other cars as well.

I can do better than 40 mpg on the highway in my 2012 Titanium Focus (best so far was 47 mpg for 92 miles round trip). It was the same technique that got me a best of 37 in my MS3, If I drive aggressively, the mileage drops accordingly. And yes, premium fuel is better than regular.

Only vehicle I could easily pull 40 mpg in was a 3-speed neon with fluttery windows. Any speed over 70 was torture. I’d have to work at it to get 40 mpgs from any of these rigs.
I think they should modify the city/highway calculations. Highway should be based on a steady state of 70 mph and city should be a constant quarter-mile stop start for two miles with A/C on. It would represent the best and the worst mpg numbers and be more representative to real world driving.

I usually get over 40 on the highway in an automatic 2004 Corolla. It drops down to the low 30s in town though. My 2002 manual Civic EX (shorter gears) averages about 38 whether in town or on the freeway. I would be surprised the new crop of compacts couldn’t break 40 mpg.

I’m also with Duncan and angrystan. With my ’06 Corolla automatic, I can fill the tank to the brim, drive from Farmington, NM to Phoenix via Heber and Payson, a 400 mile trip, and use only 2/3rds tank of gas in either direction. I can set the cruise at 60 and get over 40 mpg. This round trip is 98% highway at least until I hit PHX. If I go faster, then I burn more fuel – of course.

I’ve got a ’10 Civic with the stick also, and I’ve seen better than 40mpg on a couple occasions, although it involved sticking pretty faithfully to the speed limit. Under more typical (aggressive) circumstances, I’m still hovering around 34-35mpg, and it takes winter tires for me to drop below 30.

Under optimal conditions you can in the right car, but that’s not very likely to happen. I once got 34 mpg in my ’04 Subaru WRX, but that was driving at at steady 55 mph with no A/C on a cool night. I had also got as low as 16 mpg in the same car, so yeah, results can vary greatly.

You wouldn’t need to tailgate any trucks. Just drive 60 on flat ground with the cruise on & you will get 40+ (while driving like this–not while accelerating up to speed or overall averaging including non-hwy driving) with most compacts nowadays.

I got over 40 in my 2007 Corolla driving 60 on country two-lanes for a few hundred miles in Arkansas. Somewhat less on the interstate, say 36 or so (after the tire swap).

When I replaced the stock tires with ones that had better grip (so that I could go over 5mph when it rains) I lost about 2 mpg. average.

My Golf TDI has returned 38-46 on the highway, but you specifically excluded diesels.

I am agree that combined mileage over the life of the car is the most important metric. With the sticky tires the Corolla struggled to make it past 30 when in-town driving was included.

PAVEMENT MATTERS. Some concrete and asphalt mixes are more/less “sticky” than others and that and general condition conspire to affect mileage. Rough pavement and even small undulations in the road surface will negatively impact mileage. The Interstate between here and the next town has many overpasses and gradings that conspire to knock-back mileage on an otherwise flat route. I wonder if the people who test cars on “real-world” streets might not take that into account.

As a total aside, I saw a near-mint “curbside classic” at the gym the other day: a 300CD coupe. The seats looked like they had never been sat in. Remind me, why is it that I bought a new car?

With the cars I have in my garage (nothing special) I routinely get better than EPA highway results in mixed LA driving. But I’m pretty sure most people can’t be bothered to drive “lightly” and avoid rushing to signals, which very rarely gains you more than a car length or two.

I feel it’s my duty to save fuel and stick it to the Arabs and oil companies, while not polluting so much. And it pays off at the pump.

I’ve gotten 50mpg on the highway in my ’93 Festiva. I’ve also achieved over 40 after I swapped the engine to a more powerful Mazda BP. It seems strange that such an old car can outperform these modern subcompacts. I know they have become much heavier, but is that the sole reason for their low mpg figures?

I can usually get 10-20% more on the highway than the old EPA estimate. Our current fleet: VW Passat Wagon, 2003, HWY 31, actual, 33-34; Ford Freestyle, HWY 27, actual 30; 1995 BMW M3 Lightweight, HWY 27, actual 29. The car I owned that exceeded it by the largest amount was a 1988 Civic that returned the HWY estimate of 37 fully laden at speeds averaging 80 mph. In normal use, 45 mpg was the norm.

I took a friend’s Prius to the mountains, and, driving like maniacs, we achieved 48 mpg – just 3 less than the EPA estimate. Driven sedately, I have no doubt we could have exceeded the EPA rating.

I made a couple of trips from Edmonton Alberta to Springfield Oregon. The first time was on a 63hp Toyata Tercel, I got a trip average 36 mpg (imperial). The trip along the Columbia river was interesting, I got 2 mpg better mileage with the windows rolled down.

Our family finally got a decent car (a Mercury Sable), and we did the same trip a couple years later with the same 36 mpg with 1 additional passenger. But at least got to enjoy things like cruise control, air conditioning, an additional 73 hp, and some measure of soundproofing.

Well, my Honda Pilot beats its EPA hiway number (20) even running the AC in the summer and at 70. But it ain’t 40. Problem is most people don’t, as a regular matter drive long trips such that they use an entire tank of fuel driving exclusively on the highway.So, you rely on short-term segments and imputed calculations from the car’s computer. City mileage is hugely affected by temperature and the length of each trip. If you make a bunch of little trips in cold weather so that your engine barely reaches operating temperature before you shut it down, you’re going to use a lot of gas and be very disappointed in your mileage. Sometimes, I think engine block heaters should be standard equipment even for cars not used in frozen north places like Minneapolis. Even in mild climates like mine, it would greatly reduce — if not eliminate — warm up time in the morning, resulting in a fuel saving, and I don’t think they use much electricity.

Oh, and my modified 1968 VW Karmann Ghia got a steady 30 mpg on the highway between here and Houston (at 70) in 1973, running a Holley “Bug Spray” 2bbl carb which was jetted a bit lean. Of course, the car weighed 1500 lbs. and had no a/c.

My household’s experience is from the other side of the line– my wife has an original Prius (gotten in 2001) that has averaged north of 42 mpg overall using lots of a/c and without any special attention to driving economically. I have a 2010 tdi golf (manual) that’s gone on three multi-week road trips with epic highway legs. We load it with bags, a kid, and 3 bikes on a rack, use lots of a/c, and make good time on the highway, but still average 42-44 mpg on the trips. If north of 40mpg is gonna be a no-brainer, hybrids and diesels clearly have the edge.

Highway is one of those words that’s so broad as to not mean anything. Which highway? How fast? Whichever highway and however fast, it’s unlikely that the results will match the EPA’s stationary simulation of 0-45-0-70-0-80-0-35-10-35-0-35-0-35-0-50-0 (really, look it up) idiocy except by coincidence.

Consumer Reports tests all of their cars on actual interstate at 65 mph where most models exceed their EPA highway rating by a fair margin. Most of the current generation of poverty boxes break 40 mpg on that test. The 2012 Civic showed 47 mpg.

Whether or not a car with EPA 40MPG highway gets exactly 40MPG anywhere (particularly in a “mixed bag of city, highway and even mountain driving conditions”) is entirely beside the point.

The purpose of EPA mileage estimates is to enable consumers to *compare* cars, not to calculate their precise fuel costs. It’s important to know that the Civic beats the Cruze.

And honestly, anyone who’s not smart enough to realize that the “40MPG highway” number might not apply to his 4 mile stop-and-go commute is going to get (more or less) equally disappointed by any car on the market, so why sweat it?

The discussion point should be how well the EPA numbers correlate to real world numbers. Given the influence of the standard cycle as defined by EPA it is possible that manufacturers optimize to the EPA cycle rather than to real life driving. If different manufacturers do this to varying extent on different models the relation between EPA numbers and real world performance would vary and the value of the EPA numbers as a tool for comparison is reduced.

I’d be fine with an inaccurate EPA test as long as it was consistently inaccurate. It appears that greater controls need to be in place to prevent gaming.

To add to the questions posed by Ed above, I would add that I wonder when a backlash will occur against overly optimistic trip computer MPG reports. Car makers would love it if people became too lazy to calculate their own MPG at the pump.

I bet the EPA’s multi-mode test pattern is a throw-back to the days of carbs, points and condensors, non-ECU controls, and transmissions with 3-speeds, non-locking torque converters, and hydraulic shift circuits.

Perhaps it has been updated somewhat, but such an updown cycle would seem to be designed to test the efficiency of all these primative systems…

I’d be interested to hear from somebody who knows if this is the case…

That depends on how patient you are. In perfect dry conditions with no great altitude differences and a patient driver that is prepared to keep the cruise on and not to go over 60 should be able to get the 40 MPGs. Heck, under those (rare) conditions I can get 34 MPGs in my 335.

I have a 1995 Explorer (2wd) rated 14-18. I get 17 and 22. On occasion it can get 29mpg. At 55-60mph all interstate.

I had a 2000 Ford Contour (2.0 four/automatic) rated 19-28. I got 17 and depending on how far you drove it on the highway, anywhere from 25 to 42. First two tanks of all-higway driving were 24-25mpg, after that it would hit 39-42 mpg.

I also had a 1986 Pontiac 6000-STE (EFI 2.8/3 speed auto) rated 17-28. I got a consistent 23mpg no matter how fast or slow I drove it. Drive it 55mph- 23mpg, drive it all in town stop and go- 23.

My 1977 Chevelle (305-2bbl/3 speed automatic 2.56 rear axle) I think is rated 13/18. I get 15 with no A/C and 12 with A/C. It also gets 20 with no A/C and 18 with A/C on the road. Course that old Harrison A6 compressor will cool a small house quickly. In town with that sucky axle ratio it really hurts it. I had one similar to it long ago with a 3.08 ratio and it would knock down 15 in town easy with A/C on and get 18-19 on the highway.

All depends on how you are driving it. There’s a dude on the Explorer forum that managed to eeke out 32mpg consistently on his 00 Explorer.

I used to manage 22-24 highway in my 4Runner when I lived in an area with fairly light traffic and was running the worthless factory Bridgestone Duelers. And 17-18 around town, compared to the 16-20 EPA rating.

When I moved across country to an area with lots of stop and go traffic and upgraded to a set of grippier Generals, my mileage dropped to about 15-20 or so.

There’s so many factors. Driving style, traffic, road conditions, etc. And what kind of rubber you’re riding on is huge…so many hybrids and high-MPG specials rely on low rolling resistance tires for an extra boost, but you pay a price in traction that just isn’t worth it.

Then there was my Mustang GT with the optional 3.73 rear end that wouldn’t hit the 17-26 MPG if you dropped it off the Chrysler building. Of course, that car didn’t exactly lend itself to conservative driving habits…

the mileage on my Explorer went up when I put Michelins( better traction) on it, replacing BFG Long Trails (not terribly grippy, though did just fine on ice). It’s got 290,000 miles on it and the last road trip I had it on, it averaged 21mpg over 500 miles with 3 people and heavy traffic for most of it. In town the last tank I had on it got 19mpg running back and forth to work.

The Contour was capable of outstanding mileage, but it was such a noisy touring car for me that I’d rather have paid the extra gas for the Explorer to be comfortable. I think if I hadn’t had the automatic version it’d been a different story, but I picked it up on a whim, fixed it up some and sold it a year later for a tidy profit. It was a fun car in the twisties, but the road noise for sure would have driven me insane, it never really endeared me to it.

The Chevelle…. Well I’ve optimized the 1977 controls on it, replaced the original pellet-style cat with a modern unit, tweaked the 1950s carb to the limit, advanced the timing to help wake it up. It went from 9mpg when I got it, to averaging 15 overall. It became a game to see how much I can push the OE equipment, I think a Quadrajet is in its future as the 2 barrel isn’t that good at fuel metering at small throttle settings.

Here’s a good one for you. Back in 2000 I had a 1997 Contour V6 with the auto. I traveled a lot with that car, and usually I averaged 29 on the highway. June of 2000 I filled the car up in Erwin, TN, and drove 112 miles to Middlesboro, KY. This trip included climbing Clinch Mountain, and I drove it like I would any other time. I noticed that when I got into KY the gas gauge hadn’t moved, so I stopped and topped it back off. Turns out I only used 2.2 gallons over the course of 112 miles. Never happened again, but it sure was nice…

Yeah, that is weird. I’m not making any assumptions in your case, but in aviation, we measure fuel by lbs. rather than gallons to account for temperature and barometric pressure differences. Temp and baro can affect fuel density, so gallons (or liters) can be thrown off if you purchase fuel in Phoenix at 1100 feet MSL at 90 F and then purchase fuel in Heber, AZ at 7500 ft MSL at 65 F. So calculating mileage based on fuel purchased at those two different locations may give you bogus data. Also, if you’re running your car under a load climbing a mountain, your exhaust pipe heat may heat the fuel in the tank somewhat throwing the measurements off when you refilled later. Dunno…

The mileage ratings are just for comparison purposes. In my Jetta TDI I’ve averaged 40 but had tanks ranging everywhere from 33 mpg to 54 mpg, all depending on the temperature, how fast I drive, the mix of city to highway, etc.

I agree hybrids and diesels have an advantage, but it shouldn’t be that hard. My ’83 Quantum Coupe could get 45mpg driven at a steady 55 mph, and averaged 38 with a heavy foot and pushing AC.

I get about 35 MPG, ~80% highway, in my ’02 Civic. I’ve got a lead foot, and you’ve really got to wind the non-VTEC D17 for it to get out of its own way. But the car’s paid for and perfectly presentable, so I really don’t care about an extra 5 or 10 MPG.

Besides, I think the ideal compromise is a cushy midsizer with a larger-displacement four. I’ve bummed a 2.4L ’05 Camry for numerous road trips and that thing will do 34 MPG all day long at 70 MPH, with minimal road noise and a cushy ride. Yeah its boring, but I’ll take boring over some high-mileage little grind box or a crap-MPG “sporty” car on a 12 hour interstate slog.

Never heard of anyone who couldn’t beat EPA numbers with a TDI. On my Commutes From Hell I still get high 30’s, on normal days 41-42. What is it about diesels that they consistently seem to meet or beat the sticker, while gas vehicles so often fail to measure up?

I just drove a rented 2011 Ford Focus SEL hatchback from Las Vegas to Rachel, Nevada last week. The computer showed 36-38 on the way to Rachel, and a steady 42 on the way back. The hatchback is supposedly the least aerodynamic body style on the Focus. On the way back, my economy was probably aided by a slight downhill grade, maybe a little wind and the fact that I was drafting a UFO. I’m just kidding. There was no wind. It was a nice car. I’d consider buying one. The Sync (non touch) radio was not rental-friendly.

I wonder how many of the posted MPG claims above are actually properly calculated and how many are just going off the computer?

If, as I suspect based on the phrasing, most of them are just readings from the on-board computer then they are pretty much useless and a waste of bandwidth posting them.

Any MPG calculation should be manually calculated and based on brimmed-tank to brimmed-tank and is meaningless unless conducted over several tankfuls as there are just too many variables involved in shorter distances.

Further, taking a few “internet warriors” experiences, even if properly calculated, as being in any way representative of what a certain vehicle’s average might be is utter folly. I’d bet I’d get 10% better than any one of you but that still wouldn’t be particularly meaningful in the scheme of things.

Any MPG calculation should be manually calculated and based on brimmed-tank to brimmed-tank and is meaningless unless conducted over several tankfuls as there are just too many variables involved in shorter distances.
To be really accurate, you have to use the same pump with the car in the same position. If the car is at a different pump and parked at different fore/aft side-to-side angles, it will change the angle of the tank and effect the maximum capacity.

Any MPG calculation should be manually calculated and based on brimmed-tank to brimmed-tank and is meaningless unless conducted over several tankfuls as there are just too many variables involved in shorter distances.

Why? The fuel metering in a modern direct injection vehicle is extraordinarily accurate, the car’s computer should know exactly how much fuel was consumed to a greater degree of accuracy that you would doing it manually.

The posters on the VW TDI forum who have compared their manual calculations with the computer generated numbers report about a 3-5% variation or so, with it over sometimes and under other times so that over time it all washes out. Manual calculation can be accurate if you do it correctly and consistently but the computer readout is so much easier!

I’ve kept fairly detailed fuel consumption records for my 350Z using that method, and the delta between the trip computer’s average and the mechanica average, is around 3-5%, unless I’ve made a very sudden change in driving style right before getting gas.

When I bought my E30 off of a friend, he was telling me it got 42 mpg. He calculated it by filling the tank to full and comparing the difference, but since he odometer was broken, he’d get the miles from the freeway signs that tell you how far to the next city. It was quite a bit off…using a GPS unit, I’ve found the car actually gets between 27-30.

On my Mazda 3, I can take the trip odometer’s, divide that by the computer’s Avg. MPG, and get gallons used that is quite close (within .1) of how many gallons will go into the tank. So I would say that the computer on the Mazda is quite accurate.

FWIW,

1. Fill-ups are almost always at the same place.

2. When the auto-stop clicks off, I do not add any more, so the fill-ups are consistent.

My best MPG performance vs. EPA estimates was 28.8 MPG in a 2006 Dodge Grand Caravan, rated under the old scale at 26 highway. That was actual and matched the computer exactly (for a change). That was 100% highway 65 MPH max (due to fog limiting visibility), lightly loaded, fresh synthetic oil, K&N air filter 35 lb in the tires tires, 65 degree outside temp, so no air conditioning. If my minivan could do almost 29 under ideal conditions, I don’t see why a modern economy car couldn’t do 40+.

I would have thought you guys would have called BS on this logic:
As driven by the media over a mixed bag of city, highway and even mountain driving conditions . . . numbers do underscore the fact the 40 mpg figure is an illusion.

how do you go from 40 mpg hwy to 40 mpg for cityhighwayandevenmountain?

of course it’s good to know highway numbers, this way you can estimate your . . . highway driving costs. i know how to exceed advertised highway numbers but i don’t want to drive that way. but 33 mpg light mixed in maine on 230 c kompressor coupe was nice. i am sure it was above the advertized.

And while we’re at it, can we call BS on MPG? I’m no Europhile, but L/100 km (or GPM, if you prefer) is a much more useful measurement. Let me put it this way: in terms of fuel consumption per mile driven, which I think is what really matters, the difference between 15 and 20 MPG is the same as the difference between 40 and 120 MPG. So the difference between 38 and 40 and 42 is pretty much nothing, and any cost savings will be trivial compared to differences in other costs of ownership. I know I’m not the first reader to make this point, but this whole 40 MPG thing is just as ridiculous now as it was during the Seventies, and I guess I am getting tired of it. If you need to save money on gas, just don’t buy a 3-ton behemoth. Period, full stop.

About 6 weeks ago a gas station attendant kept on putting gas (an extra $1.50) into my 04 Civic EX 5 speed after the pump clicked off . Next fill up yielded 40.5 gallons , but when the nozzle is removed right after the pump shuts off I usually get 35 MPG driving 85% highway with the occasional 36-37 . My 09 Suzuki V Strom 650 usually averages around 55mpg with an occasional 60+ depending on the trip taken – casual cruise or fast back road blast. It’s why I got rid of it’s 1000cc big brother . Well that and the excessive vibration and balky clutch !

[quote]”Highway is one of those words that’s so broad as to not mean anything. Which highway? How fast? Whichever highway and however fast, it’s unlikely that the results will match the EPA’s stationary simulation …”[/quote]
Thank you, Mr. Clinton

The closest i ever got was 36 mpg in my 1976 honda Accord when it was new.

Mom’s mid-1980s Toyota Tercel got 45 highway and broke 50 a couple of times. That’s calculated from tankfuls, not usage computer (there wasn’t one of those). Of course that was with the 55 mph limit, and no AC (there wasn’t one of those either).

One of the reasons I bought my TDI Jetta wagon was the the TDI gets better mileage than it is rated in the real world where as most cars do not. I get about 42 MPG with a Auto Jetta wagon driving around 75 with the AC and about 85 % highway. Could I do better most likely but I will not change how I drive for a extra mile or two.

I have a 2009 MINI Clubman, 6-speed manual, non-turbo, and have 41.0 mpg on the computer read-out (averaged since I bought the car new). I’ve double-checked this by actual fill-up/mileage calculations and it is accurate. I don’t drive particularly carefuly, but I live in rural Nevada, which is at a high altitude and mostly fast 2-lane highway driving. However, several times a month I visit Reno or Carson City or visit the SF bay area for a few days, so mountain and city driving are added into the mileage mix. I just finished a 3,500 mile road trip to Denver, Dallas and back, where I was typically driving 65 to 85 mph and the computer went from 40.9 to 41.0 mpg during the trip. I like the MINI.

I have the same car, can get 40 running on real gas (no ethanol), keeping the speed about 60-65 mph. That’s computed the old fashioned way, after filling the tank. Love the Mini. You must drive all highway, my average according to the computer is about 33 mpg.

My 1973 Ford Pinto 1600 stick shifts gets 34-42 miles per gallon highway depending on the speed and temperature. It consistently knocks down 37 mpg at 65 mph every week. Slow it to 55 and stay off surface streets and you will crest 40 mpg. You will see it regularly running I-75 & I-94 through Detroit every work day when I am not in China.
Picture link: http://www.flickr.com/photos/29396384@N05/4784736813/in/photostream

I have two Audi 5000’s. My 1984 automatic FWD Avant only gets 20-22 mpg highway while the 1987 stick shift Quattro gets a real 30 mpg highway even though the computer says 34. I will place the 1987 Quattro in storage to replace the Pinto as my driver next summer.
Link: http://www.flickr.com/photos/29396384@N05/6270316159/in/photostream

Sweet Pinto I’m surprised to hear there is a 1600 powered unit still on the road as a DD. My first car was a 73 Pinto Runabout but it had the 2000. I went to 14″ wheels as 15″ in the 4 bolt pattern weren’t really available in the early 80’s. I wasn’t shooting for MPG though I was going for traction. With a little rolling of the fenders and a slight touch of trimming I was able to fit 235/60 front and 245/60 rear even with the lowering.

Virtually all cars for sale at the moment are capable of exceeding their highway estimates, sometimes by 5 MPG+, if you drive 55-65 MPH on a highway cruise. I can get 33 MPG in my 2.3L 2006 Ford Focus…according to the EPA, I only get 28 MPG.

As someone else mentioned, Consumer Reports does a highway trip and they usually kill the EPA estimate.

What really burns my ass is the fact that “B-Segment cars don’t get better gas mileage than C-Segment cars” has become a industry talking point when it’s not true. Consumer Reports often finds that these cars receive better fuel mileage than their C-segment counter parts. For example.

Ford Fiesta: 32MPG combined
Ford Focus: 28MPG combined

Mazda2: 33MPG combined
Mazda3 i: 30MPG combined

Honda Fit: 33MPG combined
Honda Civic Sedan: 30MPG combined

Now you may be saying, hey – 3 or 4MPG isn’t a lot of difference. But the difference between the 4-cylinder full-size sedans and the C-segment cars is usually 3 to 5MPG.

I suspect there’s a lot of simple denial here. Most Americans want big cars, not small ones – and they choose to skew mileage so that it appears to support their choices.

I haven’t run the numbers in a while, but the smart car has a lifetime average mpg around 41-42 and it just rolled over 45,000 miles on the way home tonight. It has gotten into the low 50s a few times on pure highway runs in good conditions. It would do better if it wasn’t such a brick aero-wise.

This useage profile represents more or less lead-footed driving style, with everything in the mix from fat low-profile Potenzas to Conti-winter Contacts, a/c, sunroof & windows open or closed, passengerless 50 kmh city cruising to hours-long cruise-control-on full-throttle 150kmh cruising (down to 130kmh in regulated areas) on the autobahn w 2 people and a tail full of luggage inside (this looks like 7.25 = 32.4 mpg).

I’m pretty confident that if I wasn’t into the turbo all the time, upshifted sooner, and kept to 100 kmh = 62 mph on the autobahn, I could do 40 mpg w/o any other adjustment or limitation.

After 6 years of keeping track, my TDI has never given me less than 42 mpg and has gone as high as 48 mpg. I’m usually in the 44-46 range and that’s after 220,000 kms and not driving in any particular style. Actually, more leadfoot than anything else.

Here’s a question I haven’t seen addressed; does the EPA do their testing with ethanol-free gas?

I recently got rid of a ’03 Mazda 6 V6 with 123,000 miles but before getting rid of it, I did a 500 mile road trip in it. EPA highway rating was 27. My best tank prior to this one was 27.5. I filled up with ethanol-free gas, and at 80 MPH with the A/C running, I almost did the whole 500 miles on one tank and got 32.5 MPG.

Everybody talks about driving style to improve mileage, but I think the ethanol in our gas is one of the reasons almost nobody gets their stated mileage.

Is there much ethanol-free gas available? The one website that tells you where ethanol-free gas is available can’t list hardly any stations in my area – and I live in the 12th largest city in the US. And of course we know that ethanol is not a good economic proposition.

I have an Acura TSX 6-speed manual – I used to get about 35 mpg on the highway a number of years ago – now the best I can get is about 32 mpg. I think it is due to the change of gas formulation – more ethanol.

“Is the only way to get 40 MPG highway in a diesel or hybrid?”
~~~~~~~~~~~~~~~~~~~
Your inquiry was the exact question I sought to answer with my past two vehicle purchases. Best MPG was 52 hwy on a 2000 Jetta TDI. The 2009 replacement obtains lower efficiency, possibly due to the added quarter ton it hauls around. In real world driving I can still exceed 40 with two kayaks on the roof.

My last fill-up of my ’06 Jetta TDI (5MT) – drove 958 km, took 52.3 litres. 5.46 L/100 km, 43 mpg US. This is very close to average for this car. Mostly highway (115 – 120 km/h), some secondary country roads (100-ish km/h but with occasional stops at intersections), driving without any particular attention to economy.

I know that by going 105 km/h (65 mph) it will get near 5.0 L/100 km (47-ish mpg US) but I can’t normally drive that slow.

I’ve seen 6.7 L/100 km (35 mpg US) with my very unaerodynamic and not particularly light motorcycle trailer in tow, by setting the cruise at 100 km/h.

edit: My dad has a 2011 Golf TDI (6-speed DSG automatic) and his consumption in normal driving is about the same as what I see.

i rented a 320d in Germany recently. 49.9 mpg on the computer and as observed. The bmw turbo diesel is a work of art, not wasting an erg of the $10 gallon diesel. Ran well at a steady 110 mph too. Who needs a hybrid ?

…i saw fourty miles per gallon on the highway all the time in my nineteen-ninety geo prizm, with no particular care to how i was driving whatsoever: just normal steady-state cruising between fill-ups…admittedly, that was the better part of twenty years ago, and cars have grown much heavier since, but surely with modern improvements in aspiration efficiency it’s not particularly unrealistic to see similar fuel economy in modern compact cars…

Some pretty impressive numbers here. The best I’ve seen on flat and level highway in my 2010 Maxima was 34 MPG. That was 55 MPH, steady running, and not insubstantial effort to breathe on the pedal. Cruise control at the same speed is good for 31 MPG. Somewhat aggressive driving at 75-85 is closer to 24 MPG.

I’ll chip in for volvo and an old 96′ lexus es300. My new T5 volvo is rated 20-30 but in mixed driving around the city I never see much above 24, on the high ways of texas in the summer it takes a nice tail wind and a slope to get above 30 mpg but I imagine that not having to use the AC as much would help. The lexus was rated at 18-27 and never saw anything above 20 in mixed driving, mostly getting around 16-17 mpg with copious amounts of freeway driving.

Lately I have been commuting on my bicycle so whenever I get in my car I tend to give less of a crap about the gas mileage and enjoy myself a little too much once the drive train is warmed up. Figure I save enough money not commuting in it to joyride once a week!

My 95 SOHC 5sp actually hit 38.5mpg and 39.5 mpg going through eastern PA, which no sane person would call flat, while going 75mph with the AC on. There is no on board mileage computer, so these were hand calculated. This was also a base model with no cruise control.

Mine did not even have AC, and in fact it was the “EX”, lightest possible 96 (even ACR was a shade heavier!). I’m wondering if you had a 1:22 non-boosted steering or something. The 95 was the only year of 4-lug wheels, too. Or simply altitude of Wyoming and Utah made it burn more (OTOH the air resistance is also reduced with altitude).

Download Gas Cubby for your smart phone and you get rid of all the cherry picking and pump kick-off variables.

2010 4Runner 4WD: 13 months of operation, 18000 miles, 805 gallons, 22.17mpg lifetime average, $0.15/mile. It is rated at 17city/22hwy. Most of my mileage is 70mph interstate for weekend travel. Next largest bar on the pareto is my commute, which is short enough that I barely get up to normal operating temps in the winter, but it is non-stop, 55mph highway. Flatlands, like Ohio, I can push 25. That isn’t the norm, though. 22mpg is a pretty consistant tank for me.

In other states where the ethanol is less, those numbers are generally bumped by 2-5 mpgs. The little Saturn got 38 mpg through Virginia and North Carolina.

I think the question “Is the only way to get 40 MPG highway in a diesel or hybrid?” is a very valid one and one that we’ve been asking for while now. Truth seems to be the big oil companies simply do not want to provide or sell diesel (make more money with reg gas), car manufacturers are very skiddish to sell diesels after the GM disasterous 350 V8 mod that everyone remembers as being revolting in every way, and the American consumer is loathe to buy something that isn’t throughly marketed.

…and the fact that diesel engines effectively are being legislated off the road with increasing emmisions regs (thank you CARB/EPA). The devices to make them run cleaner eat into their efficiency to where you can no longer offset the higher price of diesel fuel.

True, but I would argue that the oil lobbys are pushing these “stringent” emmissions regs in order to keep diesel from being a viable option. Take a look at who votes for those regs next time, you may be surprised.

40 mpg is real in our 2011 Elantra, under most highway conditions and semi-legal speeds. Leveling out the terrain and dropping it to 55 mph brings you within spitting distance of Transport Canada’s rating of 48 mpg (4.9 litres/100km), but I’ve never been able to sustain 48 mpg in real-world conditions.

Things change quickly in heavy stop-and-go conditions, however. As in 20 mpg. So I’m not surprised that people report 30ish in mixed driving.

I don’t know how 40 MPG became the ‘magic’ number for fuel mileage. The marketing folks could fixate on some other number just as easily.

Also, judging from the posts on this site, that if we all kept to out best driving practices, I think we’d all hit our car’s EPA numbers, or be pretty darned close to them.

I know with my most recent new car, our 2009 Pontiac G6, I’m somewhat disappointed with the Interstate mileage results. The car is supposed to return 33 MPG highway. I routinely see 30 MPG highway, but like so many others, I’m also routinely driving 10+ the speed limits.

I believe the brand of gasoline matters a little. Shell appears to net me better mileage than other brands, but I haven’t documented it – which would make an interesting study.

Out of necessity, I have slowed down considerably on my new commute. I set the cruise around 63 and stay in the curb lane, especially in the morning when it’s dark, as my eyesight isn’t the best at night.

At least my nerves are intact and the stress level is almost nonexistant!

@Zackman: I can attest to the brand of gasoline making a difference. In the wintertime, if I use ‘off-brand’ gasoline, my G6 will make a weird odor upon cold start up. It’s not like anything else I’ve ever noticed from a new car. When I questioned the dealer tech about this, he produced a list of Top Tier gasoline brands, and asked us to use those for a month to see if the odor went away.

I did, and the odor lessened by a large amount. However, I never noticed the odor in the summertime. My only guess is that we are still getting 100% gasoline in the summer and that the winter blend gasoline with ethanol must be producing the odd odor. Once the cats warm up, the odor goes away, but the first time it happened, I was a little concerned…

I’ve seen you post some good numbers for your Impy at other times, I was wondering how fast you were going to get those numbers. My old Maxx could generate some pretty good mileage numbers with the 3.5 V6/4 speed autobox combo. The outlier was the 37 MPG run I got coming back from Cleveland several years ago. It was this time of year where you don’t need A/C and we caught good weather (the winds coming off of Lake Erie were light)and I think it was just me and my wife.

More often at that time we’d have the car loaded up with kids and luggage, but it still managed high 20’s/low 30’s. I was never disappointed with that car.

I know for a fact I’d get better mileage if I could keep my foot off the pedal…

I got off track with the comments about the Top Tier gasoline and the odor issue. I meant to add that the times I used the Top Tier gasolines it seemed I was getting better mileage out of those tanks. I can’t say for certain, as my wife drives the G6 and relies on the trip computer for mileage. She doesn’t like to do the math, I guess.

On our recent trip to St. Louis in mid-August, I acheved the 35.44 mpg, two of us, some luggage, A/C on, keeping speed between 64-70 mph, but usually at 65 mph. Coming home we avaraged 33.69. I used Shell on the way out, Mobil coming home.

Due to visual limitations, I have to be extremely careful and not do anything stupid like sudden lane changes, so I drive currently in the curb lane, as there isn’t heavy traffic – the only benefit of my new commute. Yeah, it kind of stinks, but that’s how I gotta roll! At least my nerves are calm!

I drive with a very light foot, ’cause I hate wasting good money on gas, so that, too!

According to my Father-in-law (of course taken with a huge grain of salt) who’s worked as a quality control projects specialist for oil/gas/coal etc, refineries all pump out the same gas for whatever state regulation is required (for example, Colorado has an 85 octane base gasoline). If the various companies do something different to the gas, its not at the storage and distro site. All trucks regardless of company, pump up at the same trough. Now, that’s not to say they don’t add something to the tank prior to filling, but its doubtful.

09 Honda Fit with slushbox. Best was 42 from Ann Arbor to Dublin, OH, driving 70 in MI, 65 in the police state. This was with four-up and luggage! Worst was 33 and change from Pittsburgh to Ann Arbor into a strong west wind, winter tires, three-up and luggage. Hills and a headwind really affect the little egg. Oh, and even after the TSB reflash to correct the overly-optimistic MPG display, the thing still indicates higher than my calculated mileage.

I’m amazed at the numbers everyone else seems to get. Driving styles must be much more sedate in other parts of the country; only having lived in MA and central FL, I figured hey, everybody must drive like that.

Keeping up with traffic, my Civic turns 3500-4000RPM on the highway in 5th gear. Always wondered why they didn’t make 5th tall enough for “actual” freeway speeds, but I guess me and everyone I share the road with are outliers.

Considering my 32MPG comes virtually regardless of my driving style, (I’ve tried driving slowly (not slowly enough, apparently) and aggressively on different tanks and saw 32.7 and 32.04, respectively,) I cannot imagine what I would have to do to see 40+.

Civic MPG suffers more from drivers sense of style than driving style. Wings and body kits, oversized wheels, high power stereos and high wattage headlight bulbs can take a significant toll on the fuel economy.

If none of these apply to you and your ride, kudos. Maybe verify that you’re running 5W20 vs 10W30 – that was good for 4-5 mpg for me in the winter.

I don’t know about 40 mpg, but I do know that I can easily best the EPA numbers for my 2006 TSX. The ratings are 20/28. I never clock in under 21 MPG in local driving. On the highway I can set the cruise control at 65 MPH and get 30-32 MPG all day long.

“As driven by the media over a mixed bag of city, highway and even mountain driving conditions, the following overall mpg results were obtained:”

The key phrase is right up front there. Jack Baruth counts as a member of the media. Somehow I doubt that he and his ilk are the sort of drivers likely to get good fuel economy.

A friend of mine has one! Pretty nice gearbox, too. He got it used. Gets pretty good mileage in it, but of course he drives as though in no big hurry to get anywhere and is really, really, good about getting the shifts just right.

I went shopping to trade in my ’98 F250 in 2008 for a small B segment car, having in mind the little sport backs I remember from the ’80s. A practical car that wasnt a PITA to maintain, feed, or shoe, could take a lot of abuse and could fit the kids and the dog if necessary. Of course with this formula I wanted and expected a slick 5 or 6 speed manual, as God intended for small cars. What I found, especially in the Korean makes, was a definite lack of manual, row-it-yourself, vehicles on the lot. The sales manager always looked bemused by my request for a proper 5 speed insisting that the automatic was the best deal. Do people hate driving so much that they wish themselves into an automatic? Are Americans so lazy that we can no longer learn how to actually drive a car? Or is it car manufacturers/dealers find it to be more convenient to have the more expensive automatics lounging in the lot? For myself, I’d rather save the $800 – $1200 for an automatic for leather and a better stereo.

I’ve actually made money on the two vehicles due to buying a 2004 Civic Hybrid on the cheap for $3500, and then trading an IMA battery on a wrecked Insight for $500 and a battery balancing along with other related items on the Civic. I made a bit over $2500 on that Civic.

Subtract $2100 for the Insight I bought for parts. Add $500 for the IMA battery, $900 net for the parts sold on Ebay…. and subtract $500 again for maintenance on both vehicles.

Okay, the math is all over the place. But what I end up with is a $1300 net gain. Let’s round it down to $1000 for arguments sake.

90,000 miles, 50 miles per gallon, and -$1000 in net maintenance costs.

Until TTAC starts getting long-term testers that will be pretty hard to beat.

It’s all about driving style. I have a Cruze Eco manual and am getting 30 mpg city (most of my driving) and have seen 50 mpg highway. I don’t hypermile or do anything special. I drive the speed limit, stay in the right lane, and pay attention to traffic.

My crapcan 1998 Escort ZX2 with a manual transmission pulls 40pg actual (tank average) at its upper range if I get a solid two days of commuting with clear traffic and can stick like glue to the 70mph notch.

Of course, with minor variations in traffic pattern and driving style, the same car will quickly fall off to 35mpg, then 30, and indeed 25 on a bad-traffic Thursday/Friday combined with pressing social engagements that require excessive foot-burying on the clear stretches of road

Short answer, the 40mpg hwy is hogwash. The only to obtain such mpg out of a gas engine is to dramatically reduce weight, and being small vehicles in the first place, severely compromising safety.

I once had a 2000 Jetta TDI that I got 57mpg actual on a trip from the Twin Cities to Grand Marais, MN, and that was with screwing around in Duluth for a couple hours up and down-hill.

For example, my ’08 Malibu with 4cyl Ecotec records an average of 23-25mpg (unless it’s below freezing, last winter I got 20-22mpg with mostly highway driving). While my ’97 Accord in the same driving averages about 33-35mpg (2.2 automatic).

In my experience, domestic automakers have always exaggerated their MPG ratings to sell cars, most car guys/girls know historically they are less efficient.

I look forward to the new EPA ratings of combined MPG. It, in my opinion, will be ‘put up or shut up’ time.

Our communter-can Yaris sedan with the slushbox pulls 38-44mpg on road trips. Every time, no hypermiling required. Always above 30 in the city. The EPA is 27/35.

I’m sure a number of cars are now engineered to game the EPA test without delivering real world performance, with fingers being pointed at Hyundai and Chevrolet. But we’ve owned a number of Toyotas and a Honda, and each has easily exceeded EPA estimates.

I can’t speak to the possibility of getting 40 mpg because, with the exception of a rental prius a couple years ago, I haven’t had access to a car capable of it. As far as the relevance of the split numbers, they do matter. By the EPA’s calculations, at least 77% of my mileage is highway miles (that’s the split I have to set to get my cars real world fuel economy, and based on my driving, that’s probably reasonable), so a car’s gas consumption there means more to me than it’s city, or the combined (which might be more equally rated). An excellent illustration is Car and Driver’s recent subcompact comparison. The real world fuel economy for most of the cars was pretty similar, and pretty close to the city mileage (which was also roughly the same across the board), which would seem to indicate that sort of driving. However the Fit’s highway mileage was dramatically lower than everyone else’s, most likely due to its lacking a 6th gear. This is an issue for me and is what disqualifies the Fit from my consideration. However, if I only did city driving, that woulidn’t be a problem, and the Fit is reasonably close to the competition in city mileage. If I looked at its 5 mpg difference in combined score (to the Accent for example), I wouldn’t know that, and might disqualify the car.

On the flip side, a V-6 Mustang is down 5 mpg combined to the Fit (dragged down by its 19 city score), but only 2 on the highway. 5 mpg might make me think twice, but knowing the amount of highway driving I do, why get the Fit to save gas when I could have the Stang and get so much more car with it?

So, despite being rated far lower than everything else, the Fit is right on par with the actual loop numbers, which means, no, the Fit doesn’t need a 6th gear for gas mileage. The 6 speeds (Sonic, Accent, and Rio) generally were at the city rating on that loop, the Yaris and Versa hit about the middle of their city and highway number, and the Fit got the highway number. I have a friend with a 5MT Fit and his driving generally yields high 30s on the highway despite the 33mpg number. Looking at the 30-50mph times in top gear is another eye opening stat. 25.4 seconds in the Sonic! The rest are in the 5 to 14 second range.

IMO, if the car makes a lot of low end torque, 6th gear is a nice way to reduce fuel consumption and still have sporting gears in between. In these tiny engines that don’t make much twist, you don’t see much benefit in adding a super tall OD.

My point is the fact that these cars are all close to their city numbers would indicate that the loop driven was the equivalent of city driving. Only a driving loop with more highway driving would expose the Fit’s deficiency in fuel economy there resulting from its lack of a 6th gear (as you can see, it isn’t that far outside the mainstream in city mileage, but way down on the highway). If you don’t get up on the highway at high speed, then the tall top gear won’t do you much good. In my case, with a commute that involves a lot of driving on the fun side of 70 mph, it does matter. As far as passing times go, I’d question the real world applicability of these numbers. Yes it shows the torque to gearing ration pretty well, but any of these cars would have to be downshifted to pass from 30-50. Hell, when I’m passing 30-50 in my Dad’s BMW 328i, I’m downshifting. I’ve driven a Fit and I definitely wouldn’t leave that car in top gear to pass. As has been noted, a lot of this is dependent on your driving style. If your friend can get an extra 5 or mpg out of his Fit, who’s to say he couldn’t do the same with a Sonic or Accent? The EPA numbers are helpful in comparison purposes, even if actual results may vary (Car and Driver, in the same issue as I recall, beats the EPA numbers highway numbers in a VW Passat TDI).

You think the 750 mile test loop was the equivalent of the EPA city test cycle? That would take 35 hours of continuous driving. Even the EPA’s ‘highway’ test cycle would involve over 15 hours of driving to total 750 miles. The nice thing about the Car and Driver comparison tests is that they do provide real comparisons for cars driven in similar empirical conditions. The EPA tests are on a dyno and have next to nothing to do with the real world, right down to using fuel that most of us can’t buy. Even the EPA knows it, to the point that they artificially lop off correction factors to keep people from being angered by believing the results of ridiculously arbitrary tests that cars are tuned for to the detriment of their real world efficiency and performance.

Read the city and highway test regiments. The highway test barely involves real urban speeds, and the acceleration rates involved could be exceeded by 5 ton garbage trucks.
http://www.fueleconomy.gov/feg/fe_test_schedules.shtml

Had a 1984 Audi 4000S 2-door that would get about 44 MPG on a 65-mile commute between Denver and Colorado Springs, including the climb up 7,352-foot Monument Hill. A little googling shows a curb weight of 2,182 lbs, displacement of 1.8L churning out 85 less-than-thrilling hp. But it was fun to drive. Not really relevant to the question asked but interesting to think about. There were no airbags and you had to crank the windows and sunroof by hand, which was maybe why it could be economical and fun.

I had a Saturn Aura rental car with the 3.5L V6 that got 37 MPG (using tank full/divide method, not trip computer). I was so shocked by the MPG I thought it was a 4-banger and opened up the hood and was even more stunned to find the very thirsty GM 3.5 under the hood. That was a lot of 75 MPH driving too in central California.

@Hypnotoad: My daughter just purchased a used 2007 Saturn Aura XR (with the 3.6 V6/6 speed)recently, and we took the whole family over to Cleveland for a wedding. I drove part of the way, and while fiddling with the trip computer, I came upon the instant mileage and it was reading in the high 20’s. I was surprised, as the Aura was getting as good mileage as my Ecotec/6 speed Pontiac G6!

So, on the way back, I decided to do the mileage the old fashioned way. We filled up in Cleveland, and then when we got home. I did the math and we were getting 29 MPG on that trip. I’m no Mario Andretti, but I don’t like to wait, so I’ll drive long stretches of the trip at 80 MPH when I can get away with it.

Granted, this is an isolated trip and she will have to run the numbers for a few more months to see how the car really performs. But it wasn’t bad for a car that held all four of us comfortably and could zip down the road at any speed I set.

The EPA should specify fuel economy at a steady 70 mph with the air conditioning on as a somewhat conservative real world “highway” driving condition. I usually drive about 80 mph because gasoline is cheaper than food, lodging, or my time.

I got consistent 28mpg mixed out of my 1986 Ford Sierra 2.0IS, and steady 32-35 on highway driving, Ok, so it was a lightweight car (by todays standard) with pretty decent aerodynamics, but the engine (essentially a 1970 Pinto engine with mid eighties EFi ) was discontinued in 1990 because it couldn’t keep up with emission standards (which, as far as I understand are not as strict here in Europe as in the US ?) So I can’t understand why any midsize/compact car today should not be able to do 40 ? Aerodynamics , drivetrain loss and engines has all improved since ’85, and weight does not matter much on steady highway speeds…

Not at all, the Sierra managed well over 40 imperial IIRC :P
An early 80’s Golf 1.5 diesel (manual), although it may be one of the slowest cars ever built, can average 45-50 mpg (US gallons). Mid 90’s Escort 1.8 diesel the same. But later the diesel folks got tired of being slow, and put turbos on everything. Still, a BMW 530d can do over 40pmg, and it’s not slow by any standard.

Today’s cars are heavier and more powerful. Today’s engines are more efficient, but that increased efficiency is being put to other uses.

and weight does not matter much on steady highway speeds…

Sure it does. At highway speed, the primary determinant of fuel consumption is the energy needed to pull the car through the headwind created by the speed. That requires power, and power production burns fuel.

Aero drag does not consider the vehicle weight in any way. The only drag that considers weight is rolling resistance which is significantly smaller than aero drag at 70mph. Once you get your lump up to speed, there is very little drag difference between two identically shaped cars.

http://ecomodder.com/forum/tool-aero-rolling-resistance.php

Punch in 3500lbs and 4000lbs, copy the results to excel, and compare. At 25mph, the 4000lb car has 10% more drag than the 3500lb car. At 70mph, the 4000lb car has only 3.5% more drag than the 3500lb car.

Do you wonder why the GM piggies (Equinox, Sonic – relative to their segment) manage to have impressive highway EPA ratings that go straight to h*** when you start adding anything other than ideal conditions (occasional speed changes, mountains)? The weight is causing that. But, where is the incentive to drop weight when the EPA test lets them throw a big ol’ 32mpg rating for their FWD CUV that also rides better than the 500lb lighter competition? (also, thanks to weight, as confirmed by Bob Lutz himself).

As said at steady highway speeds, aerodynamics matter a lot more than weight, which is also why my ’93 BMW 525IX got better highway mileage than my current CR-V, even if it weighed roughly 450 pounds more. CR-V beats it in the city/+day to day average though :)

You have it backwards. All things being equal, the most important factor is weight. The engine has to pull the mass, which requires energy, which burns fuel.

Take two identical semi-trucks that are pulling trailers. The fully loaded truck will require more than 50% more fuel per highway or freeway mile/ km as would the same truck that is pulling an empty trailer. The weight makes the difference.

Pch101;
A physics rule:
A mass in motion will continue that motion unless acted on by some force. So if we ignore aerodynamics and friction, weight will have no effect on energy required to maintain speed on a flat road. Of course weight will have some effect on tire and bearing friction, but nothing too great.

So at speed, aerodynamics and engine/transmission/torque converter drag will have a larger effect on efficiency than weight. Until we go up a hill.

A physics rule:
A mass in motion will continue that motion unless acted on by some force.

The next time that you’re driving, take your foot of the accelerator and see what happens. (I’m pretty sure that you know what happens; without power to the wheels, the vehicle is going to slow down and eventually stop.)

You’re misapplying the rule. For the sake of this discussion, the friction is a constant. Only modest improvements can be made to the drag, given the profile of vehicles and their inherent drag.

What’s left is the engine’s need to pull the mass of the vehicle. The more weight that there is to pull, the more energy that is required to pull it. As noted in the example with the trucks, the weight makes a considerable difference.

PCH – the car slows down when you take your foot off the gas because drag is acting on the vehicle. If there were no rolling resistance (derived from weight), drivetrain, or aero (derived of cd & frontal area) drag, the car would continue moving at the same speed with zero add’l power. We live in a world with friction, so we have to consider all these different drags.

Your examples are looking at semi trucks. It appears the example you’re noting is about the efficiency when the truck is empty (15000kg) to full (42000kg) in the 42t trailer example. In automobiles, we’re comparing a 2800lb car to a 3200lb car if you’re looking at the compact class. That is an order of magnitude difference! The results from the your link aren’t applicable when discussing cars that only have a 15% difference in weight between the lightest and heaviest examples. The lightest to heaviest samples in your link have a 180% difference. Again, look at the link that I posted above and start punching in some numbers. When you put car numbers for weight, drag coefficient, and frontal area in, the weight, which impacts rolling resistance drag only, plays an insignificant role at 70mph. When you punch in the semi-truck numbers from your link, weight does play a huge role because the weight swing between empty and full is so huge and the weight of the truck itself is so massive compared to a compact car.

For example, not changing drag coeff, frontal area, etc., the 15kg (33k lbs) truck has 75% of its drag forces made up by rolling resistance. 25% is aero. Now punch in 3000lbs (chevy cruze). 78% of the total drag is aero and only 22% is rolling resistance.

the car slows down when you take your foot off the gas because drag is acting on the vehicle.

But there will always be drag, regardless of the design. So at the end of the day, that leaves us with the need to have an engine that can pull the weight through the drag.

Your examples are looking at semi trucks…That is an order of magnitude difference!

The point isn’t the magnitude. The point is to illustrate that weight impacts fuel economy because power is required to move the mass of the vehicle.

The same laws of physics apply to cars. The 3,000 lbs. compact needs more power if it is to have the same performance characteristics as would a 2,000 lbs. compact. To produce that power, energy must be consumed.

In the modern era, we have opted to build heavier cars with better performance numbers. Both of those require additional power. That power production burns fuel.

Even if the engines of today are more efficient than those of 20-30 years ago, that efficiency is being devoted to pulling more weight and producing more power. In the real world, there is no way to reduce drag to enough of a degree that improved aerodynamics can significantly lower fuel usage. Any vehicle that is designed to hold people, their stuff, and the engine required to propel them is going to have a profile that produces some amount of drag. Moving all of that requires an engine, and when that engine needs to move more mass, more fuel is going to be burned.

So, a 10% improvement in weight (rolling drag) makes a 2.4% improvement in overall drag. A 10% improvement in cd (aero drag) makes a 7.6% improvement in overall drag. So, yes, I agree, weight does impact fuel economy. At 70mph, though, aero drag has more “weight” to the overall drag equation. We are likely reaching the limitations of how much we can reduce the drag coefficient due to the inherent shape of the passenger volume in a car, but knocking 300lbs out of your compact sedan has a small overall impact on the highway fuel economy number. Numbers sell cars, so until it becomes financially viable to use light weight materials in a car, auto maker have no incentive to really reduce the weight of their vehicles. It is easier, and cheaper, for them to tweak the aero and run lower rolling resistance tires.

Just for fun, I put in your hypothetical 2000lb car, keeping aero at 0.30 and comparing to the original car.

Car 4 – 333 – 71 – 403 – 16.96

Only an 8% improvement over the original car. Yes, a lighter car means that you can run a smaller, more efficient engine and keep the same acceleration performance, but people have spoken with their dollars that they prefer the heavier, safer, less expensive, more stable, and more powerful compacts of today than the ones of the early 90s. I don’t like it; I’m sure you don’t like it, but it is what it is. I’m just putting the data up there that shows that dropping a bunch of weight doesn’t improve the EPA highway numbers as much as tweaking the aero and that is why automakers do what they do.

@pch101
i was talking about daily driven passenger cars in general, offcourse the weight matters, but not so much at a steady pace as it would in city driving with acceleration and deceleration all the time. Doing 60 on a highway will not cost you much more in say a early 90’s Audi A6 than in a Sierra, even if the Audi weighs 5-600 pounds more, if they both have a 2 liter engine, where as the difference increases alot in city driving. On the other hand, aerodynamic differences increases substantially only once you go over 50-55 mph, so for city driving aerodynamics are almost just a waste of time and space. Most modern passenger cars today land around (or below) a 0.30 CW (not adjusted for frontal area) Which is also the main reason CUV’s are un-economical. (My CR-V as stated uses more on the highway than my near 4000 pound BMW 525IX, even when the BMW has a 192 hp straight 6.)

Today’s equivalent is more than 50% heavier. The delta is more than 1,000 lbs., not a couple of hundred pounds.

You will find similar figures for a wide array of cars. The trends have occurred industry wide.

The modern car is also more powerful. Some of that power goes toward performance — the modern car is quicker and faster. But some of it is going to move that extra half a ton worth of weight. If the engine of the modern car was installed into a body as light as the old car, the fuel economy and performance would both be improved (although at the expense of NVH and safety.)

The 2012 Golf is also 14″ longer, 8″ wider, and 6″ taller than a 1975 Rabbit. I owned an ’07 Golf GTI and one of my best friends has a ’91 Jetta GLI. The interior space isn’t even in the same ballpark and even the A2 platform is quite a lot larger than the A1. Despite them sharing the same name, it really isn’t fair to compare the two cars. I mean, wouldn’t a Yaris (2300lbs) or a Mazda 2 (2200lbs) be a more fair comparison? Similar size, similar power to weight.

@pch101
I think that we’ve reached a point where we all agree that weight plays a significant role in fuel efficient. But you’ve gone on to label those of us who point out that weight plays a small role in constant speed efficiency as wrong. Let me repost

“Sure it does. At highway speed, the primary determinant of fuel consumption is the energy needed to pull the car through the headwind created by the speed. That requires power, and power production burns fuel.”

This sure sounds like a description of aerodynamic drag to me, and yet you wrote it as a rebuttal to this quote:

“and weight does not matter much on steady highway speeds…”

so, in fact, you agree with the aerodynamics crowd – you just don’t know it!

I think that we’ve reached a point where we all agree that weight plays a significant role in fuel efficient.

That’s a relief. Just hours ago, some folks here have treated me as some sort of fuzzy-minded heretic for even suggesting such a thing (despite the fact that you’d be hard pressed to find a qualified researcher who disagreed with my position.)

But you’ve gone on to label those of us who point out that weight plays a small role in constant speed efficiency as wrong.

What I’ve pointed out — correctly — is that this theoretical “steady state” on which you hang your hats does not exist on the planet that we live on.

“Highway driving” ≠ “steady state.” Highway driving is not synonymous with precisely constant speeds on perfectly flat terrain, contained within a vacuum with perfect and never changing conditions. Compared to “city driving”, it suggests higher average speeds and fewer complete start and stops, not precise consistency.

The subject of the thread was the EPA highway test. I posted a link from the EPA that shows the methodology of that test. There is nothing “steady” about it.

so, in fact, you agree with the aerodynamics crowd – you just don’t know it!

My argument was apparently not understood. My point is that the aerodynamics of a car can’t be changed enough to matter.

In the real world, the primary drivers of fuel economy are weight and power output. In the real world, the easiest ways to make cars use less fuel per distance driven are to reduce their performance and reduce their weight. However, both of those changes would come with a price that would be unacceptable to many of us, which is why it doesn’t happen.

Zyko … I’m getting a bit confused now by your MPG quotes because you seem to be flip-flopping from Imperial to US.

Whatever, I’ll say this….BS on 40 MPG in a Sierra!

I drove 2.0i Sierras in the 1980s and 30 MPG IMPERIAL was pretty good going unless you REALLY nursed them. As a busy sales rep I’d be lucky to get better than 25 MPG imperial in REAL driving. Sure, on weekends when I was paying for the gas (well, sometimes LOL) I might get over 30.

It may depend a bit from year to year model changes, but the 1985 and 86 IS with the 3.92:1 rear diff seem to have been quite economical compared to same year Ghias with the ‘normal’3.62:1 rear. And the later facelifted models with Cat’s were even worse (not to mention slower. As I said i averaged 28, and got 35 US gallons straight highway driving. (which in Norway means hills and turns, but usually e speed limit of 50-55 mph) Last one is calculated going on holiday with a fully packed and loaded car, with 150.000 miles on the clock which had never experienced anything remotely close to nursing in it’s then 25v years of abuse. My last Scorpio/Granada (’89) with the exact same drivetrain (but taller rear wheels) averaged 25 US gallons, and just over 30 highway (but that was a really pampered, although severly rusty 250.000 mile car.)
ps, even my carburated wreck of a 2.0 5 door that i got suspiciously cheap got more than 25mpg imperial, while being abused….

Just replying to my own post here to clarify something, or ask people to clarify;

I monitor my MPG using a spreadsheet and I KNOW what my TRUE AVERAGE consumption is spread over many years, decades even with one vehicle.

When others here say “average” I wonder what THEY really mean?

I suspect some are similar to myself but perhaps others are only referring to things like “that one holiday trip” or “a couple of weeks I bothered to check” or “I calculate it every now and then and this is what I THINK the average roughly is” and other similar scenarios.

I do (or did)the same thing, allthough I don’t keep notes. I used to calculate on each tanking on my older cars (mostly to keep up with what condition they were in, seriously if one of my non-v6 Sierras couldn’t manage 25 mpg Imperial I would expect serious engine problems) but nowadays i just calculate the two or three first tanks to get a ballpark figure for what economy I can expect for the family budget. And I like to check up on my cars on the rare vacation trips to know excactly how much I can save on just keeping a steady calm pace. Vacations are really the only chance I get to compare to ‘highway’ driving at all, normal small town Norwegian roads are B-roads at the best…
PS, I don’t add winter numbers at all, because –
1. Most of the gas is spent while defrosting and scraping ice off the windows, and
2. The rear wheels usually travel a lot longer than the car does…

2002 Honda Civic EX 5MT — best tank ever, 40.6 mpg. Best fill-up in excess of 5 gallons ever, 44.8 mpg. Best segment in excess of 30 miles ever, as calculated by ScanGauge, 49.8 (Newark NJ to Trenton NJ; 95% highway). Civic would return 36-37 mpg tanks all day long with normal, relaxed driving (keep it below 75, try to time lights) in a 80/20 highway/urban mix. New EPA is 27/33. No complaints.

2009 Mazda4 5MT — best tank ever, 30.9 (effectively all highway). Tanks vary between 23.5 and 27.5 typically. Usage cycle is a bit challenging — miles traveled are probably 80/20 highway/urban, but in terms of trips it’s probably 5 urban trips for each highway trip. Highway mileage is noticeably sensitive to increased speed (above 75, it drops like a rock) — clearly pushing a lot more air than a sedan would be. New EPA is 22/28. Only car I’ve ever driven (without obvious mechanical failures) where I haven’t routinely beaten the EPA estimates handily. Somewhat disappointed, but it makes up for it in other ways.

These are all calculated by hand, with the caveat that most all fillups are done in NJ, land of full-serv, so there’s much more noise caused by inconsistent fill procedure than there’d be if I did it myself.

Before those cars, 1993 Mazda 626 5MT (4 cyl). Best tank, somewhere in the 37-38 range; averaged about 31 over the life of the car (163k miles). All calc’ed by hand, but the nine intervening years have made the memories hazy. IIRC, it was rated about 27/33 under old EPA, and is 23/31 under the new. Great car until Brooklyn killed it.

When people recall the high mileage they achieved with cars they owned in the past, they should consider that they were running on real gasoline in many cases. Now it is a challenge in any state to buy real gasoline, and it is impossible in many states. My ’88 BMW lost more than 10% of its mileage when running on fuel that was 10% cornruption.

Good point. Also, others reflecting on ancient history is not very relevant, for instance, I had good milage in my 1980 Fiesta, but about the only NCAP-compliant feature was the break-away rubber head on the ignition key… I wouldn’t wanna crash in that car these days… no front or sidebags, airbags, belt pre-tensioners or tension limiters, abs, esp, asr, or etc. good lord, i just remembered that the windscreen was held in by a soft rubber gasket!

this is perhaps the worst pieces of reporting I’ve seen from TTAC. How is a test over a “mixed bag” of city, mountain and highway driving supposed to prove anything about if a car can achieve its 40MPG *highway* rating? The quoted source makes an erroneous conclusion from this admittedly unscientific test that the 40 MPG ratings are an “illusion”, and the TTAC writer makes no comment about that? The test was not only “unscientific”, but irrelevant, as he used a test of mixed types of driving to draw a conclusion about highway mileage! The whole point of having a city and a highway rating is to give an idea of the range of mileage a car might achieve, the buyer should estimate the mix of driving he expects to do to figure where in that range to expect the overall average to fall.

Easy guys… that was a DetN report that I quoted. Nowhere do I lend any editorial credence to its findings, nor do I make any kind of editorial point at all in the piece… as you might notice from the headline, this was a question for you all. When I write an “Ask The Best And Brightest” piece, I am genuinely looking for your input, not asking you to validate my personal perspective. Frankly, I’m baffled by how anyone can get huffy about the quality of reporting in a piece intended only to start a conversation.

And yeah, traffic does pay the bills around here. I’m struggling to think of a website that doesn’t work that way. TTAC values reader feedback as it pushes us to continually improve, but y’all have lost me with the critique here.

ok, I apologize, I shouldn’t have said “from TTAC”, the bad reporting belonged to DetN. But to the TTAC writer, why include that quote at all if all you’re looking for is feedback on what kind of mileage people are actually getting? If you’re going to include such a logically flawed quote, at least point out the obvious flaw with it so as not to appear as if you are endorsing it.

My Audi (21/28 EPA) A3 2.0T DSG averages 19 around town and 33-34 running up to LA and back.

On a 420 mile round trip recently we sat in the car-pool lane the whole way at 65-75mph. A single tank got us there and back with fuel to spare. Out of interest I filled it up and worked out the mileage.

What speed is the EPA highway number calculated at? We have a major highway here, Interstate 4, that has 50 and 55 mph speed limit stretches through town, but traffic flow in the left late will be 70-75 mph. It’s still “highway” driving, but I bet the people doing the speed limit are probably seeing at least a few more mpgs (especially in a smaller, higher strung, less powerful car since they have to work harder to push the car through the air) than people like me in the fast lane.

There is no single speed used for the EPA highway test. It varies between about 30-60 mph, with an average speed of 48 mph. It assumes no idle time, no stop-and-go driving, a warm engine at start up, and no air conditioning.

It also ‘assumes’ that you can buy real gasoline and that you will take about 15 seconds to accelerate to 30 mph. The low acceleration rates account for the absurd gearing choices and shift strategies of ‘optimized’ transmissions.

…mcs….nice bit of forensics, but I don’t know, or want to know, what a “registrant contact” is…… this is an American site, with largely American editors, writers, and viewers…… until that changes, and it could, quoting mpg, as in “miles per US gallon”, would be appreciated. None of us want a statistical Babel.

2011 Fiesta hatchback 5speed. my wife gets 38 mpg on her commute, 8 miles one way, 5 stops, 45mph top speed limit, approximately 500 feet of elevation gain and loss each way (one of the stops is at the top of a hill, one at the bottom).
On road trips we get +45 mpg.

Snow tires and winter blend gas are on the way, we’ll see how that goes.

This thread already has umpteen posts like this one, but I’ll do it anyway. My 1997 Sentra 5-speed used to always give me at least 36 on highway driving, up into the 40s with a little hypermiling. All of this was with the A/C not in use, since there was no A/C.

I have a non-S MINI with a 6-speed manual transmission. The EPA ratings are 28 city and 37 highway. I’ve had tanks of a little over 40 mpg, when most of the driving was steady speed of 50-55, with a small amount of stop and go thrown in. If I drive 75 on the Interstate, I get about 35 mpg. I haven’t had whole tanks of real city driving, but if I did, I’m sure I’d end up with well under 30.

People need to realize that the EPA ratings, and CR’s mileage numbers are useful as a tool for comparing cars, since the cars are all tested the same way, but the ratings are not going to tell you or me what we will get in our driving. That depends on a whole lot of factors.

To me, the problem is with the advertising, more than the ratings. Car companies keep talking about the highway ratings, which most people will not achieve often, if ever. I suppose they will sell some cars on the basis of the numbers, but are likely to have quite a few PO’ed customers whose driving isn’t at a steady 60 mph with no stops, or slower than that with a few stops, which is what it takes to match or beat those highway ratings.

…….as a closet hypermiler, I recognize a lot of the issues expressed, but “how gingerly do you have to drive?”
…like there’s an endangered species’ bird’s egg between the gas
pedal and your right foot
…with close attention to momentum, slowly coming out of the
throttle uphill, and as fast as possible with light throttle
downhill (factoring in speed traps)
…by never using cruise control
…by adding 5 psi to recommended tire pressures, comfort be damned
,,,windows and sunroof closed, A/C off
…never “filling up”, always pushing the envelope and ignoring “low
fuel” warnings….travel light
…ethanol free gas where possible
…skip-shift “manual” transmissions…1st, 3rd, 5th
…shutting off at the increasingly popular 5 minute traffic lights
(at least it feels that long)
…using OW/10 oil (this involves some risk of grenading)
…lots of other tips, including trying “only on TV” fuel gimmicks.
In the good old days, turning the ignition off and coasting downhill in neutral was standard practice, but the hazards involved with modern locking steering wheels make this a questionable risk/reward proposition. Getting great mpg is hard work, and a dedicated hypermiler is never satisfied……..so stop honking at them, they can’t help themselves.

When I was living in France, I had a 2004 Mégane Diesel, I was cruising at 112kph (70mph) and returning 4.2 l/100 (that’s about 55mpg US). Since then manufacturers are way more into fuel economy resulting in taller and taller gearbox ratios so getting even better results on the highway (not so sure about the city!)

Today I drive a petrol car with a very short gearbox (18.5mph/1000rpm in 5th) witch is perfect on Irish roads. Cruising at 55mph gets me 40mpg, but no more than 30mpg at 75mph (highway speeds).

Some cars like the new Chevy Sonic have ridiculously tall 6th gear, great for highway, and for sure you can reach 40mpg with that.

I averaged 40mpg driving across Nebraska a couple of summers ago, all highway miles, in my 2008 Elantra (5 spd manual). I regularly average 33+ mpg in mixed driving using premium. Every tank is calculated and there is a 5 mpg difference between regular and premium every time. If you drive a stick your driving style can hugely improve mpg.

My cousin has a 2010 Corolla with 4 speed automatic and 30K miles and says it is very hard to get 40 MPG on the open road unless she is going at lower speeds and doesn’t have to make any stops. Her window sticker says 34 highway. A good friend has a 2011 Hyundai Elantra with 6 speed automatic and well over 30K miles and says he has yet to reach 40 MPG even though the car is rated 29/40. He typically sees 35-36.5 depending on weather, outside temps and highway speed. Around town he gets 28-29 which agrees with the EPA. Another friend and car nut purchased a 2012 Cruze Eco stick which is rated for 42 highway and he actually has beat that number on many occasions and I was with him as proof on one long highway trip which netted him an honest to goodness 44.8 which we hand calculated with highway speeds in the 70-75 MPH range and temps in the 60’s. I have yet to hear what anybody has achieved with the new Civic or Focus but will keep asking around until someone gives me some answers.

I have a 1997 Saturn SL1 with 5 speed, and if I baby it, don’t go over 2000rpm, and travel 55mph on the highway (speed limit on I-465 here in Indy) I can and have made 40mpg. I wouldn’t want to do that all the time, however. I think I would go nuts doing this all the time, as I am an aggressive driver, and going 55mph on I-465 is almost signing your death sentence. I do go 60mph, and get 36mpg average.

From my experience with quite a few cars, it is easier to beat the EPA numbers, especially the city ratings, with a manual transmission. While I’m not into “hypermiling,” I generally accelerate moderately and shift early, good for getting high mpg with a manual.

Beyond that, I’ve noticed these things:

1) It’s very easy to beat the EPA numbers, both city and highway ratings, with a 1.9 VW TDI manual.

2) It’s not so easy to beat a Prius’ city rating, but, while I usually get a little less than the rated 52, I still get almost twice what I got with the car the Prius replaced.

3) It’s easy to beat the EPA highway rating with most gas cars I’ve had, when driving on rural roads at around 60 mph. Going 75-80 on the interstate, no way.

Both my ’10 Fit Sport and my wife’s ’11 Focus SEL can do 40mpg for hours on end.. Mine needs the A/C shut off(35-36 with it on), hers can manage 42-43 with it on… It helps that there’s no change in speeds(traffic) and that this part of the province is almost perfectly flat. For city mileage, I’m averaging in the low 30’s, and she gets around 33, though her “city” is more of a mix of city and highway.. My city is pure 40mph driving with lots of stupidly timed lights. My previous car (’96 TransAm) did 12 in the same driving, and her ’01 Malibu did 21-22, so we’re both saving a lot at the pump.

US gallons.. I strongly dislike both imperial gallons and Transport Canada’s way of measuring. If I can cruise at steady state of 40mph my Fit will do anywhere from 60-70 mpg once it’s warmed up.. but that only happens if i go home from work at 3 in the morning.

I had a Nissan Altima for a rental this weekend – I reset the trip computer while following a car towing a small boat, and doing 80km/h, and as I recall, it started off at 5.6l/100kms, or about 42mpg. Granted, by the end of the trip, it had dropped to 7.6l/100kms (still almost 31mpg).

I’m also wondering if the Cruze was the worst because of its turbo, and if it’d be closer to 40 with a gentle driver.

Your analysis is incorrect. The only thing the car’s engine has to overcome at a steady speed is drag, from aero and friction. Mass has nothing to do with it. Not a thing.

By your reasoning, the heavier a vehicle is, the more power it takes to keep it going at the same speed. Actually, that’s not reasoning, it’s fundamental misunderstanding of physics. Only when there is acceleration to a higher speed is extra power (and hence energy) required. That energy is one half the mass times the differences in final velocity squared minus initial velocity squared.

At a constant speed, there is no change in velocity, so the energy needed to change velocity is zero. Period. If it required energy to keep a mass at constant velocity, we’d be living in a universe where loaded freight trains could not move, being so heavy.

You have devoted mutiple replies to getting it all wrong. I normally enjoy reading your erudite comments, and have had no reason to dispute you. But this glaring error now has me wondering.

This is pretty fundamental stuff, which you obviously don’t “get”. And yes, I am both a physicist and a mechanical engineer.

The reason today’s heavier cars get worse mileage, particularly around town, is that more energy is required to accelerate the heavier vehicle to any given speed. Once at that speed, mass no longer figures in energy requirements. Change the speed to a higher one, and yes, the heavier car requires more energy to get it there. Engines have become more efficient, so if we put a new one in that antique Golf, you’d get better mileage simply because of that. At a steady cruise though, the power requirement would be near enough identical with or without the new engine.

In reference to Figure 13, if I’m reading it correct, it is saying that reducing the mass of a compact vehicle by 200kg reduces fuel consumption by 0.2gal/100mi.

So, say we’re talking about a Corolla. Knock 200kg (440lbs) off the curb weight and it will reduce consumption by 0.2gal/100mi. The highway rating of a Corolla is 2.86 gal/100mi (35mpg) normally. It would go to 2.66 gal/100mi (37.6mpg) by reducing the weight by 440lbs.

Considering the cost that would go into getting the Corolla down to 2350lbs, it is pretty easy to understand why there is more of a business case to hybridize a vehicle than reduce the weight by nearly 20%. Hybrid drivetrains recover energy lost to braking and some, like Toyota HSD, give you continuously variable gearing so you are at the most efficient engine speed and gear ratio combination. To me, it is pretty clear that mass reduction is the last thing automakers want to tackle to improve fuel economy because the cost is very high compared to the benefit with regard to how the vehicles are rated. Active aero (focus and cruze) and recovering energy lost to braking (the slew of hybrids that are coming out) is the low hanging fruit at the moment. Relatively cheap to implement and give a considerable boost to the fuel economy numbers that sell cars.

it is pretty easy to understand why there is more of a business case to hybridize a vehicle than reduce the weight by nearly 20%.

That particular article is arguing for both reducing mass, and for reducing power output to offset the performance gains achieved by reducing the mass.

That being said, I didn’t post that in order to advocate for any particular solution. I’m merely showing that contrary to what some have argued on this thread, it is common knowledge amongst researchers that there is a relationship between mass and fuel consumption. Vehicle mass reduces fuel economy, and popular compacts are much heavier than they used to be.

That’s not quite right; the car must also overcome the rolling resistance of the tires. The heavier the load, the more the tire deforms. This is significant, and heavily loaded cars can overheat their tires. That heat comes from work done by the engine.

Acceleration is the biggest downside of weight, but it takes a lot more energy to climb hills, too.

You also get the spiral effect. The heavier car requires a bigger engine, transmission, and diff, all with higher losses (imagine trying to turn the transmission and diff of an 18 wheeler with a moped engine)

The article you referenced has nothing to do with the question at hand. Did you read it?

I said exactly the same thing above. Greater mass requires more energy to accelerate it through a given speed range. So in everyday use with stopping and starting, a heavier vehicle requires more fuel. Duh. Boy, that was an insightful article!

That wasn’t the question though, was it? It was specifically about constant speed consumption.

You’re changing the question, and referencing an article dealing with another question entirely. Trying to change the subject, in fact.

Because you’re completely incorrect, and either won’t admit it, or are trying to obfuscate the situation.

The article you referenced has nothing to do with the question at hand.

You apparently missed the question yourself. I originally responded to Zycotec’s query above: “I can’t understand why any midsize/compact car today should not be able to do 40 ? Aerodynamics , drivetrain loss and engines has all improved since ’85, and weight does not matter much on steady highway speeds…”

I answered it. Today’s vehicles are heavier and produce more power. It takes more fuel to produce more power, and it takes more power to move more weight. In contrast, little progress has been made to drag coefficients, and given the nature of vehicle designs, improvements have been necessarily modest.

The “steady state” answer isn’t much of an answer. In the real world, we almost never drive in a “steady state,” even on rural motorways. The EPA highway test reflects that — the test doesn’t assume a fixed cruising speed under ideal conditions, as that is entirely unrealistic.

Although I can drive quite steadily, even in heavy traffic and on bad roads (more for comfort and car care than economy, considering I’ve mostly owned old crap cars that could theoretically collapse under hard braking or cornering) i really have to agree with you. I don’t really like new cars much at all, and one reason is they haven’t evolved as much as most other people like to think, except for safety and comfort, and the Sierra was a good car for it’s time when it comes to engine and aerodynamics (even if the rest of the car was outdated already in 1985) And off course there is a big difference between the car market in Europe and the US. 40MPG ( 5.88 liters pr 100 km) is far from an unachievable figure over here today, and considered bad for an economy or compact car, especially on highway driving.

Mass will have no effect in an utopian scenario where the road is totally flat but in the real world you are always climbing or descending somewhat.

Perhaps you can confirm, or indeed deny if I am incorrect, but I believe you will use more energy per climb than you would save on the same, so to speak, descent. I’m talking about minor grades that would not be steep enough to coast down, just your average undulations.

So mass definitely affects fuel consumption in the real world even at steady speed.

Of course, you are correct. Hills make the difference just as you say, both going up them and coming back down. That’s never a zero sum game. I was responding to the statement far above:

” ‘Weight matters when you’re in hilly and mountainous terrain.”

Weight always matters, hills or not. All things being equal, more power is required to move a heavy vehicle than is needed for a lighter vehicle. Power requires energy, and energy requires fuel.”

“…hills or not.” If there are no hills, then weight doesn’t matter, except for starting and accelerating to cruising speed. Only aerodynamic and friction effects matter at a steady cruising speed.

Correct me if I’m wrong, but we were talking about the EPA highway test in this post, which is a pie in the sky test conducted on a rolling dynamometer with suck it and see corrections, known as Krook’s constants in the trade, to try to relate the result to the real world.

On a side note, my brother lives out in Alberta, and on a recent trip from Calgary to Drumheller and back in his 2010 G37xS with four up, we got a average 7.8 l/100 klicks (30 US mpg), and only exceeded 180kmh once.:) That was as near as I’ve personally been to driving on flat land for a couple hours. Sunday, no traffic, no cops, just cruising at a high rate of knots. Great mileage. That was as near the EPA test as you can get without moving to Saskatchewan! EPA rating? 25 highway. Not bad for a heavy car with auto and AWD. In Calgary itself, the car averages 14.5 l/100 klicks, while his Astra is just 7.1, less than half the gas usage.

So, real world, weight matters because of acceleration and hills, manual versus automatic. Steady cruising, not so much

If you had a hybrid with 100% efficiency in energy recovery and re-use, car weight wouldn’t make any difference on hills at constant speed, but existing hybrids don’t have nearly 100% conversion efficiency. Still, they get very good mpg on moderately hilly terrain compared to non-hybrids of similar mass.

Highway driving on the east coast of Florida is great for economy, because the only “hills” you’ll encounter are the 30-footers you encounter when the highway crosses a surface street. I can manage to eke a whopping 25mpg out of my 8,320lb Cummins-powered dually if I keep it to 65mph on 95 between MLB and JAX…

With my 2009 Toyota Corolla base model with a manual transmission and using cruise control I get the following highway numbers driving on the highway. I drive the same 360 mile round trip on 95 between NYC and RI every other week or so, which is a fairly flat route:

2011 Jetta Sportwagen TDi: 40 mpg average on a trip to the mountains that included a few spirited runs on the Blue Ridge Parkway
2003 Jetta Wolfsburg 5-speed: About 30 MPG
1964 Oldsmobile Jetstar 88: 12 MPG, no matter what. Probably gets the same mileage at 45 MPH as it does at 115.